Thursday, November 17, 2011

"This is the first paper to provide rates of such massive extinction," says Dr. Charles Henderson, professor in the Department of Geoscience at the University of Calgary and co-author of the paper: Calibrating the end-Permian mass extinction. "Our information narrows down the possibilities of what triggered the massive extinction and any potential kill mechanism must coincide with this time."

About 95 percent of marine life and 70 percent of terrestrial life became extinct during what is known as the end-Permian, a time when continents were all one land mass called Pangea. The environment ranged from desert to lush forest. Four-limbed vertebrates were becoming diverse and among them were primitive amphibians, reptiles and a group that would, one day, include mammals.

Through the analysis of various types of dating techniques on well-preserved sedimentary sections from South China to Tibet, researchers determined that the mass extinction peaked about 252.28 million years ago and lasted less than 200,000 years, with most of the extinction lasting about 20,000 years.

"These dates are important as it will allow us to understand the physical and biological changes that took place," says Henderson. "We do not discuss modern climate change, but obviously global warming is a biodiversity concern today. The geologic record tells us that 'change' happens all the time, and from this great extinction life did recover."

That's far and away the shortest time period that I've heard for the PT. I'd be interested in what other contrasting sources have to show.

A 70-million-year-old nest of the dinosaurProtoceratops andrewsi has been found with evidence that 15 juveniles were once inside it, according to a paper in the latestJournal of Paleontology.

While large numbers of eggs have been associated with other dinosaurs, such as the meat-eating Oviraptor or certain duck-billed hadrosaurs, finding multiple juveniles in the same dino nest is quite rare.

This would be the strongest evidence yet of parental care of ceratopsians. That has been a topic of considerable arguments as of late. In fact, one of the papers in the book, Horns and Beaks, iirc, argued that ceratopsians abandoned their young to form their own pre breeding herds in NorAm. Now Protoceratops is not Triceratops by any means, but being related as closely as they (relatively) are makes it more likely that the NorAm ceratopsians gave as much parental care.

b. Sternberg Museum of Natural History, Fort Hays State University, Hays, Kansas, United States of America

c. Department of Earth and Atmospheric Sciences, and Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada

* E-mail: johan.lindgren@geol.lu.se

Abstract:

The physical properties of water and the environment it presents to its inhabitants provide stringent constraints and selection pressures affecting aquatic adaptation and evolution. Mosasaurs (a group of secondarily aquatic reptiles that occupied a broad array of predatory niches in the Cretaceous marine ecosystems about 98–65 million years ago) have traditionally been considered as anguilliform locomotors capable only of generating short bursts of speed during brief ambush pursuits. Here we report on an exceptionally preserved, long-snouted mosasaur (Ectenosaurus clidastoides) from the Santonian (Upper Cretaceous) part of the Smoky Hill Chalk Member of the Niobrara Formation in western Kansas, USA, that contains phosphatized remains of the integument displaying both depth and structure. The small, ovoid neck and/or anterior trunk scales exhibit a longitudinal central keel, and are obliquely arrayed into an alternating pattern where neighboring scales overlap one another. Supportive sculpturing in the form of two parallel, longitudinal ridges on the inner scale surface and a complex system of multiple, superimposed layers of straight, cross-woven helical fiber bundles in the underlying dermis, may have served to minimize surface deformation and frictional drag during locomotion. Additional parallel fiber bundles oriented at acute angles to the long axis of the animal presumably provided stiffness in the lateral plane. These features suggest that the anterior torso of Ectenosaurus was held somewhat rigid during swimming, thereby limiting propulsive movements to the posterior body and tail.

Tuesday, November 08, 2011

The XenoPermian Period is a fictitious, alternate geological period that takes place because we hand wave away the Permian Extinction. The assumed point of departure is that the Permian Extinction never takes place. The reason for this is that the Siberian Traps are defused and their eruptions happen over a much longer period of time. This has knock-on effects. One of them being that the world's geography is different and another being that evolution has gone in rather different directions, too.

Scott, Raven, Zach and I have been working on this for some time. We'd hoped to be further along than we are, but there have been multiple setbacks and everyone has been dealing with other projects and life in general. I either had the choice of waiting until the project was further along - which would mean probably another year - or going ahead and unveiling what we have so far.

With that in mind, I have decided to start showing off what we have. I will be putting up one XenoPermian post every other week. This will space out the posts enough that maybe we might be able to get something else done prior to the last post and reduce the lag getting new artwork done.

Geography and Areas of Interest

A world is a big place. Covering the whole world is rather difficult even in a fantasy world like the XenoPermian. This is doubly difficult because we want to give a "real" sampling of the ecologies. One of the criticisms we have for Dougal Dixon is that he does such a tepid sampling that the world feels incredibly unfinished. We realized part way through we can do better, but not even get as close as we wanted to get this done right. Even then, when we considered a better than tepid attempt, but less than boiling, we realized the world was simply too big. To that end, we settled on six places to cover, with a seventh possible if we had time (ha!). The six places are Arctica, Ural Sea, Megavongo, Transpangean Mountains, Karoo and Conan Doyle's Relica.

Let's run through the five and exhibit some of the high level characteristics of each environ and the biota there.

Arctica:

Arctica is as close to a tundra as can exist under the conditions of the XenoPermian. It has very seasonal weather. This is no surprise given that the whole environment is above the Arctic Circle. While there are some shrub like vegetation, in the form of various conifers, the vast majority of the plants present are ferns. They sprout during the start of spring as the sun moves above the horizon and then die as the sunsets for winter. Life in the north polar region is tough, albeit not as tough as Arctic of our Holocene. Temperatures hover around freezing in the winter and get quite warm in the summer. Snow dusts and covers, but no more than what can happen in, say, the Midwestern states of the US in relative spring. That's nontrivial, but not what happens in the depths of winter of our Holocene. Since vegetation is sparse in winter, most herds of animals out migrate to the more southern reaches.

Animal life is dominated thoroughly by the therapsids. While archosaurs are present, the parareptiles and nonarchosaurian diapsids are largely not. The waters are filled with temnospondyls and lepospondyls, though there are no known reptilomorphs. Despite the presence of the macrofauna, the biggest presence is actually insect and a huge number of archaic invertebrate detrivores that are active even in winter munching up the dead ferns and fertilizing for the next spring.

Megavongo:

The Megavongo is a vast outletless river delta that covers a huge area in what would have been North America. This is similar to the Okavango Delta in modern Africa, but on a far, far grander scale. Life during the dry season is much like living in a desert, even one you would fine in modern Arizona or southern New Mexico, but when the megamonsoon rains hit the Transpangean Mountains, a fraction, albeit a still vast inundation, runs down the far side of the mountains and into the dry desert. The model is much like what happens in the Ethiopian Highlands for the Okavango Delta and Nile River.

Life here is harsh and dry for most of the year. Seasonal ferns mixed with specialized horsetails and lots of seed plants, especially cycads and conifers. The most inland fringes of the delta, furthest away from the seasonal water source nearly salt flats.

The fauna here is dominated by migrants. Animals conduct impressive migrations from the foothills of the Transpangaean Mountains and the coasts of the Panthalassa and Tethys consume and breed. All clades, parareptilian, diapsid & archosarian, and therapsid participate. Of those that stay between the wet seasons, active or aestivating, there is surprising diversity amongst the clades, though shockingly low on the species level.

Transpangean Mountains:

These are the mountains that straddle and divide the vast Pangaea supercontinent. Due to the fact that the world has a lower than lower oxygen level than in our time (18% instead of 21 %), the mountains make for an interesting, but rather different biota than elsewhere. The upper altitudes are filled with archosaurs and archaic amphibians in cloud forests that get megamonsoons. The lower reaches in the rift that will eventually become the Newark supergroup, is a tropical rain forest with extremely unique mix of the clades.

Karoo:

The Karoo of what is modern South Africa also joins the mix as a temperate environment. A mix of plains, forests and everything between can be found here. Despite its name, this environment stretches all the way from one side of the Therapsids dominate southern hemisphere's terrestrial environment to the other, producing a swath of life filling the analogous role of Eurasia in our own biota.

Here, too, therapsids dominate, but the neoparieasaurs and the archosaurs have truly important additions. Vast herds migrating from along the latitudes are common here. Some that reach even from one end to the other in circular migratory paths.

Conan Doyle's Relica:

Lost worlds are a common theme. The Xenopermian is an extrapolation of the lost biota of the end Permian. Here, though, too a large single island has allowed populations of archaic forms to survive...and evolve in different directions than the mainland populations. Relica separated from the mainland during the early Permian allowing for pelycosaur grade synapsids and early parareptiles to evolve into strange, but plausible forms independent of the therapsids and more derived mainland clades. What happens when a sphenodont evolves for 60 million years independently of the therapsids and differently?

Life here is harsh and very similar in flora to Arctica, at least in analogous forms. Yet still very, very unique.

Ural Sea:

We jump back to the northern hemisphere for an environment that is like someone took the Red Sea, Tropical Forests, the coast of California and coast of Crimea and mixed them up in a massive way. Flanked in the east by the AnteUral Mountains and the West by the ProtoUral Mountains, the Ural Sea formed when the two mountain ranges that would form the future Ural Mountains caused the crust between them to buckle under rather than rise. Due to the weathering from the two mountain ranges, the sea is a very fertile and the lands, although narrow in the east-west direction, are very fertile as well, sporting a terrestrial fauna as diverse and teeming as the marine.

The reason that the Ural Sea was held to last, out of the north to south order, is that this is our first land to visit and the first

The XenoPermian Pareiasaurs, the pseudochelonids and their phylogeny, are our first graphic examples of the Xenopermian. They are excellent examples of one side of a megafaunal arms race!